1. Field of the Invention
The present invention relates to a semiconductor device having a gate structure for switching.
2. Description of the Related Art
FIG. 10 shows a cross-sectional view of essential parts of a conventional semiconductor device 400. The semiconductor device 400 is set forth in Japanese Patent Application Publication No. 2004-260140. The semiconductor device 400 is a vertical semiconductor device. In the semiconductor device 400, a pair of source electrodes 402 is disposed on a surface of a semiconductor substrate 428, and a drain electrode 422 is disposed on a rear surface of the semiconductor substrate 428. A gate electrode 410 is disposed between the pair of source electrodes 402. Actually, the gate electrode 410 is located between the drain electrode 422 and each of the source electrode 402. The gate electrode 410 switches the state of the current between the drain electrode 422 and the pair of source electrodes 402 between a conducting state and a non-conducting state.
A pair of source regions 418 is disposed on a part of a surface layer of the semiconductor substrate 428, and is electrically connected to the pair of source electrodes 402. A pair of channel regions 408 is disposed on a part of the surface layer of the semiconductor substrate 428, and is adjacent to the pair of source regions 418. An aperture region 412 is disposed on a part of the surface layer of the semiconductor substrate 428, and is adjacent to the pair of channel regions 408. The aperture region 412 extends internally from the surface of the semiconductor substrate 428, passes through an embedded region 420, and makes contact with a drift region 426. The aperture region 412 can also be called a region between the pair of embedded regions 420. Moreover, as will be described below, the aperture region 412 is a passage allowing electrons injected from the pair of source regions 418 to flow in a vertical direction. For this reason, the aperture region 412 can also be called a part of the drift region 426. The aperture region 412 can also be referred to as a protruding portion of the drift region 426. The pair of p-type embedded regions 420 makes contact with a rear surface of the pair of channel regions 408. The gate electrode 410 is disposed on the surface of the semiconductor substrate 428 with a gate insulating layer 404 in between. The gate electrode 410 opposes (faces) the pair of channel regions 408, the aperture region 412, and the pair of source region 418 via the gate insulating layer 404. The semiconductor device 400 further comprises an n+-type drain region 424 at a rear surface layer of the semiconductor substrate 428. The drain region 424 is electrically connected to the drain electrode 422.
In the semiconductor device 400, when positive voltage is not being applied to the gate electrode 410, a depletion layer extends from the p-type embedded region 420 to the channel region 408. The channel region 408 has a thickness that is easily depleted when application of positive voltage to the gate electrode 410 is stopped. When the channel region 408 has been depleted, the source region 418 and the aperture region 412 are electrically isolated, and the semiconductor device 400 is turned off. When positive voltage is applied to the gate electrode 410, the depletion layer that was formed in the channel region 408 contracts. Electrons thereby move from the source region 418 across the channel region 408 to the aperture region 412, and the semiconductor device 400 is turned on.